HVAC cleaning procedures technical questions comments, Jan 2003

NYC 9/11 Public Portal Document

A/C and Ventilation System Cleaning Procedures.

General 1. Is there a measure for sufficient negative pressure or is sufficient as defined in item 4. Of the procedures?

Some duct cleaners use vacuum collection systems that are not HEPA filtered. Specify HEPA filtered vacuum collection system and loose the commentary about asbestos contractors and duct cleaners.

Is "adequate to collect all dust" a visual observation?

General 2. Does this apply to outdoor units such as the roof mounted A/C's at 333 Rector Place? What constitutes a "containment"? Is this similar to a "tent"? Must the containment be exhausted and will it be air tested? Air handlers with heavy contamination that are in common areas, such as the fresh air ventilation system in the laundry room of 333 Rector Place, should be cleaned in some type of "containment". This "containment" could be placed under negative pressure and have poly drop cloths protecting horizontal surface, but I believe full prep is overkill. Additionally this entire space will be HEPA vacuumed and wet wiped as part of the common space cleaning. I strongly recommend adhering to DEP clearance criteria prior to reoccupancy.

General 4. This implies that any access point used to clean the riser (kitchen or bathroom inside an apartment) must have a temporary containment built? Is this the intent? If only one register is open during whipping or brushing activities (access to riser from apartment vent), and a 3000 CEM vacuum collection system is being used, the face velocity will be in excess of 3000 FPM based upon the dimensions of the grill (less than 1 sf). The offending dust is very light. With this velocity, what is the likelihood of dust blowing back from the duct? If containments are required will air testing be employed? Is the containment under negative pressure?

General 5. What are "special measures"? Insert note: Refer to item 5. under procedures.

General 6. SSC will provide additional pricing or modify pricing to include encapsulation.

Procedures 2. Although I agree with the air intake or return side of the unit procedure, the supply side procedures may not be appropriate. If it is necessary to exhaust from the roof on vertically feeding systems or as mandated by access points, cleaning may start from the grills toward the fan unit. It is more appropriate to specify that cleaning will always start and work toward the vacuum collection system rather than a component of the HVAC system.

Procedure 3. If the smoke detectors are applicable, it should be the responsibility of building management to shut down the system and coordinate with FDNY.

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